Ping "DOC" Question

I'm not Doc, but it sounds like a bad TBI gasket or something similar. Look for a major vacuum leak.

CJ

A. Throttle position sensor

B. I have noticed the throttle body itself on many TBI engines loosening. Check the 3 bolts on the top that secure it, although I doubt thats it, since it happened all of a sudden.

C. Idle air control

Buck,

Follow this link and pull the codes.

Pull the codes, let us know what you find.

Doc

Vacuum leaks don't cause black smoke (sign of running rich). Even withthe excess air from a vacuum leak the injectors just open up to even out the mixture. If he's blowing black it's an EFI component.

Doc

Inline..............

Wouldn't cause a problem at idle.

Wouldn't cause black smoke.

Wouldn't cause black smoke.

Doc

O2 sensor could have gone south, or wire shorted to exhaust pipe, will cause 'extremely lean' reading and the ECM will rich it out to the max

Have seen it the culprit many namy times causing high idle, but not the rich smoke problem

Agreed

Could easily

How ?

Magic maybe?

Doc

Thanks for the link, I'll pull the codes as soon as I can and get back to you.

Thanks,

-Buck F.

The idle air control valve works by opening/closing a trim valve to alter the airflow into the intake when the throttle is closed. If it is not allowing enough air into the engine, that would cause a rich condition. Not likely of course, as the PCM should respond by simply lowering the idle, unless through failure of the valve or sticking from extreme builup, it can't be lowered enough.

All that being said, I think the shorted O2 sensor wire sounds most likely as the problem, since it happened a few minutes after the engine was running. Perhaps the amount of time needed for the exhaust to heat up to the point where it would melt through the insulation.

He also mentioned that it still wont start. O2 wouldn't have an effect on that.

You need to take a look at the coolant temp sensor. It's located next to the thermostat, just to the left as you look in from under the hood. It should have two wires plugged into it, probably black and yellow. I'm assuming here that your engine is a 4.3 litre. Most of the time the problem is a corroded connector. Give the connector a good cleaning, then put it on and take it back off a few times. If that fixes it, great. If not, get an ohm meter and check the resistance across the two terminals in the sender. It should measure between a few hundred and a few thousand ohms, depending on the temperature. If it reads the same as an open circuit, replace it. Corrosion is far more common.

BTW, to clear out a flood and get it to start, hold your foot flat on the floor while you crank. It shuts off the injectors.